On a previous post, you can read about what protein is, what its uses are, and how the body metabolizes protein or breaks it down for energy. This is Part 2 of this couple of posts on Protein Nutrition.
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It is important to know the basics of what Protein is, not only for a better understanding of what you are consuming or eating, but more importantly to know how to fuel your body for repair and improved function. Food rich in protein, when ingested, takes time and travels a long way before it is digested, absorbed, and used by the body. Excess protein is processed again to be excreted by the body. It is essential to know which protein sources provide the complete amino acids that your body needs at a specific time, without taxing your body from processing excess protein.

This article aims to enumerate the common and best sources of protein and rank them according to their quality and how quickly they can be absorbed by the body. I included the advantages and disadvantages for each protein source so that you can decide which one fits you for your specific goal in a specific time. These ingredients can be found in food but are usually the main ingredients that are used for protein supplements. Note that the sources below refers to the protein ingredient from food sources and not to the actual dietary food that we see everyday (for example, egg protein refers to ovalbumin, the protein extracted from egg whites) unless indicated.

How do you measure the quality of Protein sources?
A laboratory method of determining the quality of a protein source is called the Protein Digestibility- Corrected Amino Acid Score (PDCAAS). The PDCAAS of a protein is internationally recognized as the best method to compare sources of Protein. If a protein source has a PDCAAS of 1.0, it means that it exceeds the essential amino acids requirement of the body and is an excellent source of protein.

Another method is called the Protein Efficiency Ratio (PER). PER is determined by comparing the weight gain of rats that were fed a particular protein against a standard protein source (egg whites).

In general, gelatin (collagen) protein and wheat protein relatively has poor quality. Meatand fishsources are moderately high-quality sources of protein. The sources of protein that have the highest quality are soy, egg, milk, whey, and bovine colostrum protein and they will be discussed and enumerated for comparison below.EGG PROTEIN (ovalbumin)
This is the fundamental protein source that we all know of. If you are a regular gym goer, yomay have heard of some big bulky guy in your local gym who gulps a dozen raw egg whites for body building. Drinking raw egg whites may sound crazy (I think it is) but it may be reasonable because egg protein is the standard of comparison or the reference point to compare and rate the quality of the other types of proteins.

Advantages of Egg Protein
Egg protein is actually extracted from whole eggs or primarily from chocken egg whites through various techniques. Studies have shown that egg protein is as effective as milk protein, casein, and whey in nitrogen retention to make lean tissue. Also, egg protein can be readily available for your daily consumption from egg whites.

Disadvantages of Egg Protein
Processing egg protein to produce ovalbumin can be expensive, and its use for the production of supplements has been reduced.

PER- 2.8
PDCAAS- 1.00

MILK PROTEIN
Milk protein has 80% casein and 20% protein. It is commonly used in supplements because milk protein is relatively cheaper. However, milk sources for protein vary in fat content and total calories, so better check the labels first and compare with other milk products if you are considering milk for your protein source.Advantages of Milk Protein
One cup of milk provides about 8 grams of protein. Milk is a fairly good source of both essential and conditionally essential amino acids. If you are lactose intolerant, you can have skim milk as an alternative, which is also a good source not just of protein but also carbohydrate.

Studies have actually shown that milk before or during (and both) exercise is an effective sport drink. Also, drinking milk after exercise encourages protein synthesis.

Disadvantages of Milk Protein
Milk sources for protein generally contains a higher amount of fat and total calories compared to other sources. Milk protein is also digested and absorbed more slowly by the body. Also, some people may be lactose intolerant which eliminates milk from their options for protein sources.

PER- 2.8
PDCAAS- 1.00

WHEY PROTEIN
Whey protein is one of the most familiar and may be the most used nutritional supplement for active individuals. There can be different ways that whey protein is processed and manufactured and it affects the fat and lactose content of the product. Some proteins found in whey also bind with vitamins and minerals, therefore making it a very useful protein source even for nutrient metabolism.Advantages of Whey Protein
Compared to other proteins, whey protein can be digested faster and is often perceived as a protein having a high quality. Some studies have also shown that whey protein may offer additional health benefits compared to casein (another protein found in milk) such as improving the immune system and preventing cancer.

Disadvantages of Whey Protein
Whey protein is one of the high-quality protein sources, but it is also a more expensive protein source. Differences in processing whey protein also slightly affects its amino acid, fat, and lactose content.

PER- 3.0 to 3.2
PDCAAS- 1.00

CASEIN
Casein protein or caseinates is another protein processed from milk. Caseinates are extracted from skim milk and can be produced as sodium, potassium, and calcium caseinates. They are common ingredients in commercial supplements.Advantages of Casein Protein
Casein is a high-quality protein source and is a very inexpensive source of protein. Supplements that have casein as its main ingredient may be relatively cheaper compared to other products, depending on its quality, taste, and how it is manufactured. Also, casein is absorbed slower by the body but this makes it produce a prolonged increase in amino acids. A notable advantage when comparing casein to whey is that casein prevents muscle breakdown (catabolism) which adds to better muscle recovery and faster adaptations to exercise and training.

Disadvantages of Casein Protein
Generally, casein is absorbed by the body much slower compared to other protein sources. It does not mix well with liquid and tends to clump, which can be an issue when it goes to your stomach. If you are in a competition and you already have butterflies in your tummy, casein protein may not be a good choice.

PER- 2.9
PDCAAS- 1.00

SOY PROTEIN
Most people may be surprised that soy is actually a high-quality protein source. Its scores are similar to that of fish and meat, and just slightly lower than egg, milk, and other high-quality protein sources. Most importantly for vegetarians, soy protein is considered the best choice for their protein source.Advantages of Soy Protein
Compared to other dietary sources like milk, meat, and eggs, soy protein is a low-fat vegetable source for protein. It can contribute to lower cholesterol levels and displaces food that are high in saturated fat. For women, soy may serve as an alternative nutrition for estrogen hormone. I once had a male client who did not want to drink soy milk because he heard from his gym that it can cause the chest muscles to increase in size but in an undesirable manner and even sag (i.e., man boobs). To explain this, soybeans have isoflavones which bind to estrogen (a specific female hormone) receptors and this binding producing estrogen-like effects. Men need not to be fearful of soy protein because men doesn’t have estrogen receptors and are unaffected by this subtle chemical reaction. To quote the book, “Little if any research exists to document negative outcomes in males ingesting soy protein in terms of training adaptations.”

Disadvantages of Soy Protein
Soy protein is not a complete protein source as it lacks the amino acid methionine. For some people, the taste of pure soy milk products can be a factor. Also, you should also check the labels on flavoured soy milk products regarding its fat and total calorie content.

PER- 1.8 to 2.3
PDCAAS- 1.00

BOVINE COLOSTRUM
Bovine Colostrum is a pre-processed milk liquid that is derived from cows during the first 48 hours after giving birth. It is mainly processed as a supplement (unless you dare drink directly from a cow’s udder) for commercial protein products.Advantages of Bovine Colostrum
Bovine colostrum has more nutrients than traditional dairy milk and also has a higher quality of protein. It also has other benefits such as improving the immune system, balancing insulin, and antibacterials which cannot be found in other proteins. Bovine colostrum has been marketed as a unique and high-quality protein source that promotes growth and enhances the immune system.

Disadvantages of Bovine Colostrum
There are only producers and dairy farms that market bovine colostrum. There also are major differences in processing bovine colostrum products. You also have to pay a little more for supplements containing bovine colostrum. More research may be needed to determine if it is a better source to whey protein.

PER- 3.0
PDCAAS- 1.00

SUMMARY

Ovalbumin, the protein found in egg whites, is the standard for comparing protein quality

The two highest-quality sources of protein are Wheyand Bovine Colostrum.

The ingredients in protein supplements can be found in dietary food. The body digests and absorbs protein differently compared to other food like carbohydrates and fats, so consuming protein supplements may be beneficial for better absorption.

Since most of these protein ingredients can be found in dietary food, it may be more prudent to eat a healthy balanced diet instead of taking in supplements especially if you are not a competitive or professional athlete.

Knowing the PER and PDCAAS rating of each ingredient would help you choose and decide which protein supplement works best for your individual needs and goals.

The way these protein sources are processed to be manufactured as ingredients for protein supplements may affect its quality.